Method for manufacturing a fibrous material impregnated with thermoplastic polymer

Abstract

A method of manufacturing an impregnated fibrous material including a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, the method including pre-impregnating the fibrous material while it is in the form of a roving or several parallel rovings with the thermoplastic material and heating the thermoplastic matrix for melting, or maintaining in the molten state, the thermoplastic polymer after pre-impregnation, the at least one heating step being carried out by means of at least one heat-conducting spreading part (E) and at least one heating system, with the exception of a heated calendar, the roving or the rovings being in contact with part or all of the surface of the at least one spreading part (E) and partially or wholly passing over the surface of the at least one spreading part (E) at the level of the heating system.

Claims

1. A method of manufacturing an impregnated fibrous material comprising a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein said impregnated fibrous material is produced as a single unidirectional ribbon or a plurality of unidirectional parallel ribbons and wherein said method comprises: a step of pre-impregnating said fibrous material while it is in the form of a roving or several parallel rovings with a thermoplastic polymer powder, the pre-impregnating being done with a pre-impregnation system chosen from among a fluidized bed or a spray gun; and at least one step of heating the thermoplastic polymer powder after the thermoplastic polymer powder has pre-impregnated the fibrous material, the at least one step of heating including melting the thermoplastic polymer powder to impregnate the fibrous material and form the at least one thermoplastic polymer matrix, the at least one heating step being carried out by means of at least one heat-conducting supporting part (E) and at least one heating system, with the exception of a heated calender, wherein said at least one heating system is chosen from an infrared bulb, a UV bulb or an equipment employing convection heating, the roving or rovings being partially or wholly in contact with a surface of the at least one supporting part (E) and partially or wholly passing over the surface of the at least one supporting part (E) at a level of the at least one heating system, wherein the method excludes any electrostatic impregnation method where the continuous fibers gain a deliberate charge, and wherein the impregnated fibrous material possesses a porosity of less than 10%.

2. The method according to claim 1, wherein said impregnated fibrous material is not flexible.

3. The method according to claim 1, wherein one or more supports are present upstream from the pre-impregnation system.

4. The method according to claim 1, wherein said at least one heating step immediately follows the pre-impregnation step.

5. The method according to claim 1, wherein said at least one supporting part (E) is a first compression roller with either a convex, concave or cylindrical shape.

6. The method according to claim 5, wherein said roving or rovings of fibrous material form an angle ?.sub.1 of 0.1 to 89? with the first compression roller and a horizontal tangent to said first compression roller, said roving or rovings expanding in contact with said first compression roller.

7. The method according to claim 5, wherein a second compression roller is present after said first compression roller, said roving or rovings of fibrous material forming an angle ?.sub.2 of 0 to 180? with said second compression roller and a horizontal tangent to said second compression roller, said roving or rovings of fibrous material expanding in contact with said second compression roller.

8. The method according to claim 7, wherein at least one third compression roller is present after said second compression roller, said roving or rovings of fibrous material forming an angle ?.sub.3 of 0 to 180? with said third compression roller and a horizontal tangent to said third compression roller, said roving or rovings of fibrous material expanding in contact with said third compression roller.

9. The method according to claim 1, wherein said at least one supporting part is made up of 1 to 15 cylindrical compression rollers.

10. The method according to claim 9, wherein said at least one supporting part is made up of six to ten cylindrical compression rollers, all at the same level.

11. The method according to claim 1, wherein during the at least one heating step the roving or rovings of fibrous material possess a spreading percentage at an outlet of a last compression roller of about 0 to 300% relative to that of said roving or rovings of fibrous material at an inlet of a first compression roller.

12. The method according to claim 1, wherein said thermoplastic polymer powder contains a nonreactive thermoplastic polymer.

13. The method according to claim 1, wherein said thermoplastic polymer powder contains a reactive pre-polymer capable of reacting with itself or with a second pre-polymer, based on chain ends of said second pre-polymer, or with another chain extender, said reactive pre-polymer optionally being polymerized during the at least one heating step.

14. The method according to claim 1, wherein said at least one thermoplastic polymer powder contains a polymer or copolymer selected from a group consisting of polyaryl ether ketones (PAEK); polyaryl ether ketone ketone (PAEKK); aromatic polyether imides (PEI); polyaryl sulfones; polyarylsulfides; polyamides (PA); PEBAs; polyolefins; and mixtures thereof.

15. The method according to claim 1, wherein said at least one thermoplastic polymer matrix contains a polymer whose glass transition temperature is such that Tg?80? C., or a semi-crystalline polymer whose melting temperature Tm?150? C.

16. The method according to claim 1, wherein said at least one thermoplastic polymer matrix contains polyamides.

17. The method according to claim 1, wherein the impregnated fibrous material possesses a fiber level between 45 to 65% by volume.

18. The method according to claim 1, wherein the porosity of said impregnated fibrous material is less than 5%.

19. The method according to claim 1, wherein the method further comprises a step for shaping the impregnated roving or impregnated parallel rovings of fibrous material into a single unidirectional ribbon or a plurality of parallel unidirectional ribbons by calendering using at least one heating calender, said at least one heating calender including a plurality of calendering grooves in accordance with the number of said ribbons, wherein the shaping occurs with a pressure and/or separation between rollers of said calender.

20. The method according to claim 19, wherein the shaping step is done using a plurality of heating calenders, mounted in parallel and/or in series relative to a passage direction of the fiber roving or rovings.

21. The method according to claim 19, wherein said at least one heating calender comprises an integrated induction or microwave heating system, coupled with the presence of carbon fillers in said thermoplastic polymer matrix.

22. The method according to claim 19, wherein a belt press is present between the at least one heating system and the at least one heating calender.

23. The method according to claim 19, wherein a heating nozzle is present between the at least one heating system and the at least one heating calender.

24. The method according to claim 23, wherein said heating nozzle covers said single roving or said plurality of parallel rovings after impregnation with a polymer powder, wherein the polymer powder is either identical to or different from said thermoplastic polymer powder.

25. The method according to claim 19, wherein a belt press is present between the at least one heating system and the at least one heating calender and a heating nozzle is present between the belt press and the at least one heating calender.

26. The method according to claim 1, wherein said thermoplastic polymer matrix further comprises carbonaceous fillers.

27. The method according to claim 1, wherein said fibrous material comprises continuous fibers selected from carbon, glass, silicon carbide, basalt, silica, flax, hemp, lignin, bamboo, sisal, silk, cellulose, amorphous thermoplastic fibers having a glass transition temperature Tg higher than the Tg of said thermoplastic polymer powder when the thermoplastic polymer in the powder is amorphous, amorphous thermoplastic fibers having a higher Tm of said thermoplastic polymer powder when the thermoplastic polymer in the powder is semi-crystalline, semi-crystalline thermoplastic fibers having a melting temperature Tm higher than the Tg of said thermoplastic polymer powder when the thermoplastic polymer in the powder is amorphous, semi-crystalline thermoplastic fibers having a higher Tm than the Tm of said thermoplastic polymer powder when the thermoplastic polymer in the powder is semi-crystalline, or a mixture thereof.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a diagram of a heating system according to the invention with three rollers.

(2) FIG. 2 describes a tank (10) comprising a fluidized bed (12) with a supporting part, the height (22) of which is adjustable. The edge of the inlet of the tank is equipped with a rotating roller 23a over which the roving 21a passes and the edge of the tank outlet is equipped with a rotating roller 23b over which the roving 21b passes.

(3) FIG. 3 describes an embodiment with a single compression roller, with a tank (10) comprising a fluidized bed (12) in which a single cylindrical compression roller (24) is present and showing the angle ?.sub.1.

(4) The arrows at the fiber indicate the passage direction of the fiber.

(5) FIG. 4 shows, but is not limited to, an embodiment with two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, with a tank (10) comprising a fluidized bed (12) in which the two cylindrical compression rollers are at different heights relative to the bottom of the tank (R.sub.2 at a height H.sub.2 above R.sub.1 at a height H.sub.1) are present and showing the angle ?.sub.1 and ?.sub.2.

(6) The arrows at the fiber roving indicate the passage direction of the fiber.

(7) FIG. 5 shows an exemplary embodiment with the tank (10) comprising a fluidized bed (12) in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side by side and showing the angle ?.sub.1, and the angle ?.sub.2=0? and the roving passing between the 2 rollers.

(8) FIG. 6 shows an exemplary embodiment with the tank (10) comprising a fluidized bed (12) in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side by side and showing the angle ?.sub.1, and the angle ?.sub.2=90? and the roving passing below R.sub.2.

(9) FIG. 7 shows an exemplary embodiment with the tank (20) comprising a fluidized bed (12) in which two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, at different levels are present and showing the angle ?.sub.1 and ?.sub.2 and the roving passing below the roller R2.

(10) FIG. 8 shows an embodiment with a tank (10) comprising a fluidized bed (12) with two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, and a compression roller R.sub.3 and showing the angles ?.sub.1, ?.sub.2 and ?.sub.3.

(11) FIG. 9 shows a photo taken with scanning electron microscopy of a cross-sectional view of a ? Toray carbon fiber roving, 12K T700S M0E impregnated by a PA11/6T/10T D50=100 ?m polyamide powder according to the method described in WO 2015/121583 (after calendaring).

(12) The method according to WO 2015/121583 shows a lack of homogeneity in several locations of the impregnated roving diagrammed by the white arrows.

(13) FIG. 10 shows the fluidization as a function of the air flow rate. The air flow rate applied to the fluidized bed must be between the minimum fluidization flow rate (Umf) and the minimum bubbling flow rate (Umf).

(14) FIG. 11 describes a tank (20) with a supporting part, the height (22) of which is adjustable. The edge of the inlet of the tank is equipped with a rotating roller 23a over which the roving 21a passes and the edge of the tank outlet is equipped with a rotating roller 23b over which the roving 21b passes.

(15) FIG. 12 shows an embodiment with a single compression roller, with a tank (30) comprising a spray gun (31) for powder (32) in which a single cylindrical compression roller (33) is present and showing the angle ?.sub.1.

(16) The arrows at the fiber indicate the passage direction of the fiber.

(17) FIG. 13 shows, but is not limited to, an embodiment with two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, with a tank (30) each comprising a spray gun (31) for spraying powder (32) and in which the two cylindrical compression rollers are at different heights relative to the bottom of the tank (R.sub.2 at a height H.sub.2 above R.sub.1 at a height H.sub.1) are present and showing the angle ?.sub.1 and ?.sub.2.

(18) The arrows at the fiber roving indicate the passage direction of the fiber.

(19) FIG. 14 shows an exemplary embodiment with the tank (30) comprising a spray gun (31) for spraying powder (32) in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side by side and showing the angle ?.sub.1, and the angle ?.sub.2=0? and the roving passing between the 2 rollers.

(20) FIG. 15 shows an exemplary embodiment with the tank (30) each comprising a spray gun (31) for spraying powder (32) and in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side by side and showing the angle ?.sub.1, and the angle ?.sub.2=90? and the roving passing below R.sub.2.

(21) FIG. 16 shows an exemplary embodiment with a tank (30) each comprising a spray gun (31) for spraying powder (32) and in which two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, at different levels are present and showing the angle ?.sub.1 and ?.sub.2 and the roving passing below the roller .sub.2.

(22) FIG. 17 shows an embodiment with a tank (30) with two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, each comprising a spray gun (31) for spraying powder (32) and a compression roller R.sub.3 comprising a spray gun (31) for spraying powder (32) and showing the angles ?.sub.1, ?.sub.2 and ?.sub.3.

(23) FIG. 18 shows a photo taken with scanning electron microscopy of a cross-sectional view of a ? Toray carbon fiber roving, 12K T700S 31E impregnated by a D50=51 ?m PEKK powder according to the inventive method described in example 2.

(24) The diameter of a fiber represents 7 ?m.

(25) FIG. 19 shows a photo taken with scanning electron microscopy of a cross-sectional view of a ? Toray carbon fiber roving, 12K T700S 31E impregnated by a D50=115 ?m PA MPMDT/10T polyamide powder according to the inventive method described in example 3.

(26) The diameter of a fiber represents 7 ?m.

(27) The following examples provide a non-limiting illustration of the scope of the invention.

Example 1 (Comparison)

(28) A 12K carbon fiber roving was impregnated with PA 11/6T/10T, as described in WO 2015/121583. D50=100 ?M.

(29) Results:

(30) The results are shown in FIG. 9 and show a lack of homogeneity in several locations of the impregnated roving diagrammed by the white arrows.

Example 2: General Procedure Comprising a Step for the Pre-Impregnation of a Fibrous Material (Carbon Fiber) with a PEKK Powder in a Tank Comprising a Fluidized Bed Provided with a Single Roller and a Step for Infrared Heating

(31) The following procedure was carried out:

(32) Pre-Impregnation Step A cylindrical compression roller R.sub.1 in the tank (L=500 mm, I=500 mm, H=600 mm), diameter 25 mm. Residence time of 0.3 s in the powder Angle ?.sub.1 of 25? Expansion about 100% (or a width multiplied by 2) for a carbon fiber roving of Toray ? carbon, 12K T700S 31E D50=51 ?m, (D10=21 ?m, D90=97 ?m) for the PEKK powder. edge of the tank equipped with a stationary roller.

(33) The fibrous material (? carbon fiber roving) was pre-impregnated with a polymer (PEKK with particle size defined hereinabove) according to this procedure.

(34) Heating Step

(35) The heating system used is that described in FIG. 1, but with eight stationary cylindrical rollers R.sub.1 to R.sub.8 with diameter 8 mm.

(36) The speed of advance of the roving is 10 m/min.

(37) The infrared used has a power of 25 kW, the height between the infrared and the upper roller is 4 cm and the height between the infrared and the lower rollers is 9 cm.

(38) The angles ?.sub.1 to ?.sub.8 are identical and 25?.

(39) The height h is 20 mm.

(40) The length l is 1000 mm.

(41) These eight rollers are each separated by 43 mm.

(42) Calendaring using two calendars mounted in series equipped with an IR of 1 kW each after the heating step.

(43) FIG. 18 shows the impregnated fibrous material obtained with PEKK.

(44) This demonstrates the effectiveness of the impregnation method by a dry powder in fluidized bed with a compression roller and controls the residence time in the powder combined with a heating step.

Example 3: General Procedure Comprising a Step for the Preimpregnation of a Fibrous Material (Carbon Fiber) by a Polyamide Powder (MPMDT/10T) in a Tank Comprising a Fluidized Bed and Provided with a Single Roller and a Step for Infrared Heating, Four Rollers Preceding the Tank (Upstream Supporters)

(45) The four rollers preceding the tank are cylindrical and stationary with a diameter of 8 cm.

(46) The rollers are 54 cm apart (distance between the first and last roller).

(47) Pre-Impregnation and Heating Step

(48) The pre-impregnation step and the heating step are identical to example 2, but the polymer used is as follows:

(49) D50=115 ?m, (D10=49 ?m, D90=207 ?m) for the MPMDT/10T powder.

(50) Calendaring using two calendars mounted in series equipped with an IR of 1 kW each after the heating step.

(51) The Results Obtained are Similar to Those of Example 2.

Example 4: Determination of the Porosity Level by Image Analysis

(52) The porosity was determined by image analysis on a ? carbon fiber roving impregnated by MPMDT/10T in fluidized bed with upstream supporters followed by a heating step as defined hereinabove.

(53) It is less than 5%.

Example 5: Determination of the Porosity Level the Relative Deviation Between Theoretical Density and Experimental Density (General Method)

(54) a) The required data are: The density of the thermoplastic matrix The density of the fibers The grammage of the reinforcement: linear mass (g/m) for example for a ? inch tape (coming from a single roving) surface density (g/m.sup.2) for example for a wider tape or a fabric

(55) b) Measurements to be done:

(56) The number of samples must be at least 30 in order for the result to be representative of the studied material:

(57) The measurements to be done are: The size of the samples taken: Length (if linear mass is known). Length and width (if surface density is known). The experimental density of the samples taken: Mass measurements in the air and in water. The measurement of the fiber level is determined according to ISO 1172:1999 or by thermogravimetric analysis (TGA) as determined for example in the document B. Benzler, Applikationslabor, Mettler Toledo, Giesen, UserCom 1/2001.

(58) The measurement of the carbon fiber level can be determined according to ISO 14127:2008.

(59) Determination of the Theoretical Mass Fiber Level:

(60) a) Determination of the theoretical mass fiber level:

(61) $\%{\mathrm{Mf}}_{th}=\frac{m_l.Math.L}{M{e}_{\mathrm{air}}}$

(62) With

(63) m.sub.l the linear mass of the tape,

(64) L the length of the sample, and

(65) Me.sub.air the mass of the sample measured in the air.

(66) The variation of the mass fiber level is presumed to be directly related to a variation of the matrix level without taking account of the variation of the quantity of fibers in the reinforcement.

(67) b) Determination of the theoretical density:

(68) $d_{th}=\frac{1}{\frac{1-\%{\mathrm{Mf}}_{th}}{d_m}+\frac{\%{\mathrm{Mf}}_{th}}{d_f}}$

(69) With d.sub.m and d.sub.f the respective densities of the matrix and the fibers.

(70) The theoretical density thus calculated is the accessible density if there is no porosity in the samples.

(71) c) Evaluation of the Porosity:

(72) The porosity is then the relative deviation between theoretical density and experimental density.